Subantarctic shearwaters, Otago

[Oscar Thomas]

Kia ora all

Today on the University of Otago NIWA Polaris II transect (water sampling and various other research activities from Taiaroa Head to 65km offshore and back) we observed 3-4 Subantarctic shearwaters throughout the day. This was great as I had never seen the species before. According to the Birds NZ they are a reportable species away from the Chathams and Subantarctic Islands. There are only a handful of records from Otago but Graeme Loh mentions that they are uncommon (but not unusual) visitors the Otago Canyons and beyond from Oct-Mar. They are also seen in Foveaux Strait around this time of year.
Other highlights were 15+ very curious Broad-billed prions, 5 Black-bellied storm petrels, 1 White-faced storm petrel, 1 Grey-backed storm petrel, 1 Snowy/Gibson's wandering albatross, 5 mollymawk species, Dusky Dolphins, 2 Grey-faced petrels, 1 Buller's shearwater, and a couple dozen Hutton's shearwaters close to the headland.

[Oscar Thomas]

A few more photos

[sjacques]

Great work Oscar, very educational for those of us tentatively learning our way around the black and white puffinus complex.

The bird in the first image looks quite pale headed, almost intermediate between assimilis and elegans to my eye. Is this down to variation between individuals, or between populations within the species' range, or some other explanation entirely?

Cheers,
Sean

[Graeme T]

Some great photos there from Oscar. I think the characters for separating these two species at sea are still not well defined. If you look at images on nzbirdsonline you will see some of the Little shearwaters from the Hauraki Gulf can appear fairly dark around the face including some dark feathers going just below the line of the eye. Yet most birds have paler faces and normally some white in front of the eye. Its been a while since I have had a subantarctic shearwater in the hand but from memory they all have black feathering below the eye like the bird in the second image. Tracking of assimilis from Hauraki Gulf colonies shows they regularly range down to the east coast of the North Island as far as the Chatham Rise and in the non-breeding season move eastwards along the subtropical convergence. None of the tracked adults went as far south as Dunedin. But who knows where juvenile birds go to. Its certainly possible both species mix off the eastern side of the South Island as there is a small breeding population of subantarctic shearwaters at the Chathams. Looking at Oscars images I think the second bird has to be a subantarctic shearwater but the first one could be either species.

[Oscar Thomas]

Cheers Sean and Graeme.
In all photos online I have come across the dark patch immediately behind/below the eye seems to be more extensive/solid in Subantarctic shearwaters. the first and third images show the same individual, so while I do think that Subant shearwaters are very similar in plumage to the Hauraki little shearwater, the pale effect on the first image seems to be a product of the light conditions and angle of the bird at the time (bright sun reflecting off what might me more iridescent feathers). A similar effect can be seen in Phil's photos in the gallery here: https://nzbirdsonline.org.nz/species/su ... shearwater